Desulfurization process utilizing ethylene polyamine and sodium hydroxide



Sept. 29, 1959 F. KING DESULFURIZATION PROCE SS UTILIZING ETHYLENE V POLYAMINE AND SODIUM HYDROXIDE Filed March 15, 1955 miotcm MZON a k mzow 2954 59? m a Em. f /N- Q Q was :9; n 2985i 2526 v Laurence E King Inventor By LU U, 7 W A ttorney United States Patent Laurence F. King, Sarnia, Ontario, Canada, assignor to Esso Research and Engineering Company, a corporation of Delaware Application March 15, 1955, Serial No. 494,431-

I 3 Claims. (Cl.'208231) The present invention is concerned with a process for the removal of objectionable compounds from hydrocarbon mixtures containing the same. The invention is more particularly concerned with a desulfurizing and sweetening process by the use of a reagent comprising an ethylene polyamine preferably used in conjunction vwith an alkali metal hydroxide. The invention is particularly concerned with the removal of sulfur compounds from hydrocarbon fractions boiling below about 700 F. with treating agents of this class.

It is well known in the art to use various processes for the removal of objectionable sulfur compounds from pctroleum oils. These sulfur compounds occur in practically all of the hydrocarbon fractions that are derived from petroleum. While the precise structure of the various sulfur compounds is not known, they are generally classified into mercaptans, disulfides and polysulfides. Other sulfur compounds, for example, are hydrogen sulfide, the thiophenes and various alkyl and cyclic sulfides. Regardless of their chemical structure, these sulfur compounds are generally not to be desired in petroleum fractions, particularly in those petroleum fractions boiling in the gasoline, kerosene and heating oil boiling ranges.

For instance, when sulfur compounds are present in a motor fuel they tend to lower the storage stability of the gasoline as well as to increase the tendency of the gasoline to form deposits within the internal combustion engine when burnt. These sulfur compounds also have an adverse effect on the octane number response of a gasoline to the addition of tetraethyl lead.

In accordance with the present invention, these undesirable sulfur compounds such as mercaptans, disulfides, polysulfides and the like are removed from a hydrocarbon mixture containing the same by the treatment with a reagent comprising an ethylene polyamine in conjunction with the relatively small quantity of an alkali metal hydroxide.

The process of the present invention may be more fully understood by reference to the drawing illustrating one embodiment of the same. Referring specifically to the drawing, a feed oil which, for the purpose of illustration, is assumed to be a crude petroleum oil, is introduced into distillation zone 1 by means of feed line 2. Distillation zone 1 may comprise any number or arrangement of distillation stages. Temperature and pressure conditions in zone 1 may be adjusted to remove overhead by means of line 3, a hydrocarbon fraction boiling below the motor fuel boiling range. Hydrocarbon constituents boiling within the motor fuel boiling range are removed from zone 1 by means of line 4. Higher hydrocarbon fractions as, for example, kerosene, diesel fuel fractions and higher boiling fractions may be removed from distillation zone 1 by means of lines 5, 6, and 7 respectively.

The hydrocarbon fraction boiling in the motor fuel boiling range is condensed and preferably washed with a caustic solution in zone 8. Fresh caustic is introduced 2,906,706 Patented Sept 29,1959

into zone 8 by means of li'ne 9 while spent caustic is withdrawn from zone 8 by means of line 10. The amount of caustic employed as well as the concentration in this initial, stage may be varied appreciably. For instance, a concentration of NaOH may vary from about 5% to 20%. and, higher. The quantity used may vary from one-half volume to about 3 volumes of caustic solution per volume of motor fuel. The caustic washed naphtha is removed from zone 8 and introduced into a desulfurizat'io'n. zone 11. In zone 11 an ethylene polyamine is introduced by means of line 22 while a small amount of an alkali metal hydroxide is introduced by means of line 24; The mixture is withdrawn from zone 11 by means of lirie12 andpassed to a settling zone 13.

Under certain conditions it may be desirable to combineth'e caustic wash and reaction zone into one. On

certain raw catalytic naphthas equivalent results are secured employing a single stage rather than two stages.

The extract phase is removed from zone 13 by means of line 14 while the treated oil is removed by means of line 15.- This'mixture is then introduced into distillation zone 16 .wherein temperature and pressure conditions are adapted to remove overhead by means of line 17, the motor fuelha'ving a lower sulfur content. This fraction is condensed in zone 18 and removed by means of line 19. The fraction may be subsequently treated or processed in any manner desirable. A bottoms fraction is removed from zone 16 by means of line 20 and handled as desired. Residual amounts of the amine can be removed from the naphtha by water washing.

The invention is broadly concerned with the use of ethylene polyamines, for the removal of undesirable sulfur compounds from hydrocarbon fractions containing the same. Suitable polyamines are ethylene diamine, propylene diamine, triethylene tetramine, tetraethylene pentamine, and diethylene triamine.

In order to effect a good separation by fractional distillation alone, the boiling point of the amine should be at lease 50 F. above the end point of the naphtha. For heavy catalytic naphthas (up to 450 F. end point), triethylene tetramine (532 F. RP.) and tetraethylene pentamine (632 F. B.P.) are satisfactory. Alternatively, an amine boiling below the naphtha range e.g. ethylene diamine (244 F.) can be used. Ethylene diamine has the added advantage that the commercial product is an azeotrope containing 25% water, which leads to a much lower solubility in the naphtha phase and thus more nearly quantitative separation of naphtha from the extract. The desulphurizing activity of ethylene diaminealkali hydroxide also appears to be superior to that of the higher amines.

These amines are used in conjunction with a relatively small amount of a promoting agent which is preferably an alkali metal hydroxide as, for example, sodium or potassium hydroxide.

It is preferred to treat about volumes of the hydrocarbon fraction being desulfurized with about 25 to 300 volumes of the amine solution containing from 0.1% to 10% of the promoter (based on feed) as, for example, about 2% of sodium hydroxide. The temperature of the treatment is in the range from about 80 F. to 700 F., preferably in the range of about 180 F. to 400 F. Sodium hydroxide content may vary from about 0.3% to 4% by weight.

The process of the present invention may be more fully understood by reference to the following examples illustrating the same.

Example I Iso-octane containing 0.17% of sulphur as di-isoamyl disulfide was treated with an equivalent volume of ethylene diamine containing 2% by weight of sodium hydroxide. The temperature of treatment was 215 F. Under thcse'conditions approximately 70% of the sulfur was removed from the hydrocarbon phase.

7 :Example- II A norrnal octane solution containing 0.14% of-sulphur as-diethyl-tetrasulfide was treated with an equal volume (if-ethylene diamine containing 2% by weight of sodium hydroxide-at atempera'ture of 230 -F. Approximately 90% ofthezsulfur waszremoved from the hydrocarbon phase.

Example III A :naphtha stream was segregated in a coking operation. This stream had a final boiling pointof 407 F. and contained 15% aromatics, 35% olefins .and 50% saturates. This stream was treated with 50% by volume of propylene diamine containing 1% by weight of sodium hydroxide at a temperature of 180 F. Under these conditions the sulfur was reduced about 43%.

What is claimed is:

1. A process for the desulfurization of a distillate petroleum fraction boiling in the motor fuel boiling range which comprises contacting said fraction with from about .25 to 3 volumes of an ethylene polyamine for each volume-of said fraction in the presence of from about 0.1 to 10% by weight of an alkali metal caustic solution, said ethylene polyamine and alkali metal caustic solution being the sole desulfurization agents, said contacting being carried out at a temperature in the range offrom about 180 to about 400 F.

2. Aprocess as definedby claim 1, wherein said ethylene polyamine is ethylene diamine.

3. A process as defined in claim 1 wherein said ethylene polyamine has a boiling point at least 50 F. above the final boiling point of said fraction.

References 'Cited in the' fileof this patent UNITED STATES PATENTS 2,152,720 Yabro'fi Apr. 4,- 1939 2 ,411,105 Nixon etal Nov. 12, 1946 2,718,454 Wylie Sept. 20, 1955 2,724,685 =Meadows Nov. 22, 1955 2;731,393 Arundale et a1. Jan. 17, 1956 

1. A PROCESS FOR THE DESULFURIZATION OF A DISTILLATE PETROLEUM FRACTION BOILING IN THE MOTOR FUEL BOILING RANGE WHICH COMPRISES CONTACTING SAID FRACTION WITH FROM ABOUT 25 TO 3 VOLUMES OF AN ETHYLENE POLYMAMINE FOR EACH VOLUME OF SAID FRACTION IN THE PRESENCE OF FROM ABOUT 0.1 TO 10% BY WEIGHT OF AN ALKALI METAL CAUSTIC SOLUTION, SAID ETHYLENE POLYAMINE AND ALKALI METAL CAUSTIC SOLUTION BEING TE SOLE DESULFURIZATION AGENTS, SAID CONTACTING BEING CARRIED OUT AT A TEMPERATURE IN THE RANGE OF FROM ABOUT 180* TO ABOUT 400* F. 